Device for guiding fine wire



Feb. 3, 1970 c, GUENEL ETAL DEVICE FOR GUIDING FINE WIRE Filed April 12. 1968 FIG/I United States Patent Int. 01. Bissh 23/04 US. Cl. 226-196 9 Claims ABSTRACT OF THE DISCLOSURE A thin metallic wire nearing a hot radiator, is guided by an orifice with curvilinear edges formed by circular surfaces which are in motion. The movement of the surfaces prevents the condensation of metallic vapors on the edges, which always remain clean and flawless.

This invention relates to a device for guiding a fine wire and for bringing the end of a fine metal wire into the vicinity of an intensely heated body, especially an apparatus for carrying out a metal vapour coating process by vaporisation of the said wire.

It is known to carry out vaporisation not by the boiling of a liquid contained in a crucible, but directly from the solid wire without a crucible. This method of operation is advantageous, since a crucible, subjected to an impregnation throughout by the liquid metal (for example aluminum), does not retain identical electrical and thermal properties, which afiects the vaporisation speed. As a result, there are irregularities in the vaporisation process. This disadvantage is obviated by vaporisation without a crucible.

The wire used, necessarily very fine (a few tenths of a millimetre in diameter) curves if it is in a horizontal or inclined position and has to be guided to the vicinity of the heating radiator. This guiding is preferably effected by means of a fine tube into which the wire enters through an orifice on issuing from a delivery reel, pressure being applied by a roller-type driving device, from which the wire issues through another orifice, at a distance of about 10 to 20 mm. from the heating radiator, in the form of a bar, for example of boron nitride.

Experience shows that guiding devices of this kind do not always operate in a wholly satisfactory manner, the outlet orifice becoming blocked during the course of a vapour coating operation under the action of local condensation of metallic vapour. As a result, the wire travel becomes blocked. Now, it is indispensable to ensure correct operation during a coating process, the duration of which may be, for example, about an hour and a half, since the process is carried out under vacuum in a chamber which cannot be opened before the end of the process without compromising the results. When a process is completed, on the other hand, the chamber is opened for discharging and re-charging, and the vaporisation device is then accessible.

In order to prevent the blocking of the outlet orifice and the stopping of the wire, the wire is guided by an assembly of at least two rotary discs which partly overlap one another, defining an orifice which is fixed in space with mobile edges, through which the wire can pass.

The invention will be described in more detail with reference to the accompanying drawings wherein:

FIGURE 1 is a perspective view showing the basic arrangement of a system for guiding wire by using two discs.

FIGURE 2 is a perspective view in exploded form showing a three-disc wire guiding device.

In FIGURE 1, two identical discs 12, 14, with parallel axes, are provided, each with a slot of circular form at 13, 15 respectively. These discs partly overlap, the illustration showing the disc 12 in front of the disc 14. The distance between the opposite faces is preferably about several tenths of a millimetre. The positions of the discs relatively to one another are chosen so as to bring the two slots 13, 15 opposite one another over part of their angular development. According to the distance between the centres of the discs 18, 20, there is obtained either a free-passage orifice through the two discs aligned on the centres, or else two intersection zones which are symmetrical relatively to the line of the centres. For an angle in the vicinity of between edges of the slots, the zone of intersection is bounded by four equal curved sides.

It is this position which is shown in FIGURE 1, with two intersection zones 16, 16' symmetrical with respect to the line of the centres 18, 20.

A driving device (not shown) causes the two discs to receive a rotational movement, for example, as indicated by the arrows f f respectively.

A fine wire 10, driven in the direction of the arrow 11 by a device (not shown) passes through one of the orifices 16.

A fixed shield in which a through hole 17 is formed is situated in front of the discs.

The rotational speed of the discs is regulated so as to permit continuous operation as long as a metal vapour coating operation lasts, for example about an hour and a half.

The edges of the slots are protected by the shield to prevent the formation of a deposit which might cause blockage.

In FIGURE 2, which shows only the necessary elements for the understanding of the invention, a fine wire 21 is unwound from a delivery reel 31, mounted on a shaft 30, for example by a clamping effect between a roller 32 driven on its shaft 33 by a device (not shown) and another roller 34 on shaft 35.

The wire 21 passes through a hollow shaft 36 which is driven in rotational movement about its axis by means of a gear rim 37 by a device (not shown). In the vicinity of the outlet end of the said hollow shaft 36, another gear rim 40 acts on three gearwheels 41, 42, 43 which are uniformly distributed over the periphery of the rim 40. Each gearwheel comprises a shaft 511, 52, 53 respectively which are each fast with a disc 71, 72, 73 respectively. Each disc is advantageously constituted by a metallic hub or central portion 81, 82,. 83 respectively and a peripheral web 61, 62, 63 respectively which can advantageously be made of polytetrafluorethylene (registered trademark Tefion). As FIGURE 2 shows, each web extends between the two other webs. 0f course, this requires arranging the webs in a slightly skewed manner.

By way of a variant, the hollow shaft 36 can be fixed and serves as a fixed support for the gearwheel 40 which in this case is driven by other means.

The edges of the three webs define an equilateral triangle with curved sides indicated at 90, through which the wire 21 passes.

The rubbing of each web between the two others ensures self-cleaning and prevents the formation of deposits which could block the orifice.

The wire 21 coming from the orifice 90 in the direction of the arrow 11 into a zone heated to a high temperature, in order to protect the apparatus which has just been described from being subjected to excessive heating the said apparatus is protected by a shield which may be advantageously be constituted by a metal disc 38 whose periphery is in close thermal contact, for example by brazing, with a tube 39 of annular form connected at its ends 44, 45 to a cold water circulation system. The shield 38 also comprises a hole 91 centrally for the passage of the wire.

What is claimed is:

1. Device for guiding a fine wire comprising at least two rotatable discs which partly overlap one another, said discs defining an orifice which is fixed in space, with mobile edges, through which the wire passes.

2. The guiding device as claimed in claim 1, wherein the orifice is formed by a zone common to two circular slots, each of which is provided in respective rotatable discs.

3. The guiding device of claim 2, wherein the two slots have at least one zone of intersection, intersecting at an angle preferably in the order of 90.

4. The guiding device of claim 1, wherein the orifice is formed by a zone bounded by the edges of said rotatable discs.

5. The guiding device of claim 4, wherein each disc comprises a central portion which is preferably metallic, and a peripheral web made of a plastic material.

6. The guiding device of claim 5, wherein the edge of one disc is slightly skewed and extends between the edges of two adjacent discs.

7. The guiding device of claim 1 further including a hollow rotating shaft through which the wire passes, a gear rim carried thereby, identical gearwheels operatively coupled thereto, and means coupling said discs which form said orifice to said gearwheels to rotate.

8. The guiding device of claim 1 further including a heat shield comprising a disc with cooling means, the centre of said wire passing therethrough.

9. The guiding device of claim 8, wherein said cooling means comprises a tube brazed to the periphery of said heat shield disc and carrying liquid coolant.

References Cited UNITED STATES PATENTS 3,279,669 10/1966 Bernard et a1. 226l96 X ALLEN N. KNOWLES, Primary Examiner 

